Despite advances in our understanding of primary lung oncogenesis, the mechanisms driving the progression from primary to metastatic lung cancer remain poorly characterized. To date lung cancer research has primarily focused on the dysregulation of protein-coding genes thereby under-representing the emerging role of long non-coding RNAs (lncRNAs). Due to recent technological advances our lab was the first to discover 120 lncRNAs, of which 35 were previously unannotated, that differentiate metastatic tissues from benign and primary tumors, termed Metastasis Associated Lung cancer LncRNAs (MALLs). Therefore, the long-term goal of this proposal is to understand how MALLs contribute to the metastatic progression of lung cancer. Our current understanding of how lncRNAs function in cancer is still in its infancy. However, several examples indicate that lncRNAs may be master regulators in cancer biology, typically binding with chromatin modifying complexes and guiding them throughout the genome to regulate gene expression. Supporting this, metastatic tumors were enriched for differentially expressed protein-coding genes targeted by Polycomb Repressive Complex 2 (PRC2). In lung cancer, studies show that the catalytic subunit of PRC2, EZH2 (an H3K27 methylase), is overexpressed, associates with poor prognosis, promotes tumor progression, and epigenetically represses genes to promote metastasis. As proof of concept, we found that the most up- regulated lncRNA in metastatic tumors that interacts with EZH2, MALL-1, promotes cellular migration and invasion in vitro, alters expression of epithelial-mesenchymal transition (EMT) markers, and cooperatively represses well-known PRC2 target genes associated with metastasis in patients. This serves as a strong rationale for our hypothesis that MALLs interact with PRC2 to epigenetically regulate genes to promote metastases. To pursue our hypothesis, in Aim 1 we will refine the landscape of MALLs that are altered during metastatic progression across a larger independent patient cohort. We will also implicate MALLs in epigenetic regulation by prioritizing MALLs that consistently interact with PRC2. In Aim 2 we will assess specific interaction sites between a PRC2 and MALL necessary to promote aggressive phenotypes and epigenetically regulate genes involved in metastasis. In Aim 3 we will confirm that a PRC2-associating MALL promotes metastasis in vivo and whether it can be inhibited therapeutically. Our studies will have a large overall impact on the field of lncRNA tumor biology by defining the landscape of MALLs altered in metastasis, providing mechanistic insights into MALL-dependent epigenetic regulation, and associating MALLs with metastatic phenotypes in vitro and in vivo. Since many MALLs are altered across solid tumors they may have conserved regulatory roles thereby broadening the impact of this study beyond lung cancer. Our study also has translational implications as the discovery of even a single MALL that could serve as a therapeutic target can spur new avenues for therapeutic manipulation of MALLs to transform lung cancer treatment.